Jet engine exhaust augmentation unit

ABSTRACT

A turbojet engine exhaust augmentation unit comprising an elongated nozzle for receiving the turbojet engine exhaust, a water injection system for injecting water into the engine exhaust for cooling the exhaust, an enlarged rear discharge conduit for discharging the cooled engine exhaust from the augmentation unit and an elongated shroud having a forward collar for close coupling the augmentation unit to the turbojet engine tail pipe and operable for returning a portion of the nozzle exhaust from the nozzle outlet to the nozzle inlet for augmentation of the jet exhaust.

United. States Patent Lemmerman [4 1 Aug. 15, 1972 (s41 JET ENGINEEXHAUST 3,591,087 7/1971 Tontini ..60/264 AUGMENTATION UNIT 6 72Inventor: Richard D. Lemmerman, P. 0. Box

192, W. Hartford, Conn. 06601 Filed: Feb. 25, 1971 Appl. No.: 118,905 gint. Cl. ..'..F0ln 33/04, 864d 33/06 1 Field of Search..-.60/264, 39.5,310; 181/33 HC, 181/33 HB [56] References Cited UN1TED STATES PATENTS 12,810,449 10/1957 Coleman .."......l81/33 HC 2,957,537 10/1960 Morgan..181/33 HC 3,011,584 12/1961 Lemmerman..' ..181/33 H13 US. Cl. ..18l/33l-IC, 60/395 Attorney-Prutzman, Hayes, Kalb & Chilton 57 ABSTRACT Aturbojet engine exhaust augmentation unit comprising an elongated nozzlefor receiving the turbojet engine exhaust, a water injection system forinjecting water into the engine exhaust for cooling the exhaust, I anenlarged rear discharge conduit for discharging the PAIENTEnmms m23.684.054

SHEET 1 0F 2 INVENTOR RICHARD D. LEMMERMAN PATENTEDMIB as 1912 saw 2 or2 0000000 9 000000666 OOOOOOOO OOOOOOOQ 22222 BRIEF SUMMARY OF THEINVENTION The present invention relates to a new and improved jet engineexhaust augmentation unit having notable utility in turbojet engine testcells for attenuating the engine exhaust temperature and noise.

I-Ieretofore it has been the practice in the operation of turbojetengine test cells to provide for the aspiration of a large amount ofsecondary or augmentation air into the jet engine exhaust to reduce theengine exhaust temperature (from for example in excess of l,250F duringnormal military engine operation and in excess of 3,400 F duringafterbumer operation) to approximately 500 F to prevent damage to theengine test cell and the exhaust silencing system. In such prioraugmentation systems it was customary to employ a mass flow rate ofsecondary air substantially greater than and in any event not less thanthe mass flow rate of'the jet engine exhaust to avoid unstable engineoperation and engine overheating. In accordance with the presentinvention the mass flow rate of secondary air is substantially reducedwithout causing unstable engine operation or engine overheating and thepresent invention therefore provides for substantially reducing thetotal massflow rate through the engine test cell.

It is a primary aim of the present inventionto provide a new andimproved turbojet engine exhaust augmentation unit for substantiallyreducing the secondary air conventionally used for augmenting the engineexhaust and for thereby reducing the required capacity 'of the jetengine exhaust. and intake air handling equipment.

It is another aim of the present invention to provide a new and improvedjet engine exhaust augmentation unit which provides for assisting inabating the jet engine exhaust noise.

It is a further aim of the present invention to provide a new andimproved jet engine exhaust augmentation unit which facilitatesconverting jet engine test cells for testing higher thrust jet engines.

It is another aim of the present invention to provide a new and improvedjet engine exhaust augmentation unit which facilitates removingpollutants from the jet engine exhaust.

Other objects will be in part obvious and in part pointed out more indetail hereinafter.

A better understanding of the invention will be obtained from thefollowing detailed description and the accompanying drawings ofillustrative applications of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a generally diagrammatic side elevation view, partly brokenaway and partly in section, of a turbojet engine test cell employing anembodiment of an exhaust augmentation unit incorporating the presentinvention;

FIG. 2 is an enlarged generally diagrammatic longitudinal section view,partly broken away and partly in section, showing the exhaustaugmentation unit in more detail; and

FIGS. 3-5 are generally diagrammatic longitudinal section views, partlybroken away and partly in section, similar to FIG. 2 and showing threeadditional embodiments of an exhaust augmentation unit incorporatingthe.present invention.

2, DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to thedrawings in detail wherein like numerals designate like parts throughoutthe several 7 figures, and referring particularly to FIGS. 1 and 2, anembodimentlO of an exhaust augmentation unit incorporating the presentinvention is shown employed in a turbojet engine test cell 12 foraugmentation of the jet engine exhaust of a turbojet engine 14. In aconventional manner the test cell 12 comprises an elongated generallyrectangular housing 20 for the turbojet engine 14 to be tested, avertical air inlet stack 22, and a vertical exhaust stack 24 havingvanes 26 for directing the exhaust upwardly through a suitable scrubbingand sound treatment unit 28 provided for reducing noise and removingpollutants from the exhaust.

The exhaust augmentation unit 10 is shown comprising a housing with agenerally bullet-shaped shroud 30 having a forward inwardly taperedgenerally conical collar or coupling 32 for receiving a turbojet enginetail pipe 16 and a rear cylindrical discharge conduit 34 secured to arear flange 35 of the shroud 30 in alignment with the tail pipe outletopening 36. As seen in FIG. 2, the forward inlet opening 37 of thedischarge conduit 34 is substantially larger than the tail pipe outletopening 36 (e.g., having a diameter more than twice the diameter of thetail pipe outlet opening 36) and the collar 32 provides for closecoupling the jet engine tail pipe 16 to the augmentation unit 10 with,however, suitable spacing between the tail pipe 16 and collar 32 topermit air flow between the collar 32 and tail pipe 16 to cool the tailpipe and provide a small amount of secondary air for augmenting the jetengine exhaust.

An elongated generally cylindrical tube or nozzle 38 is mounted withinthe housing 30 by vanes 39 intermediate of and coaxially with the jetengine 16 and discharge conduit 34. The nozzle 38 has a forward throat40 substantially larger than the tail pipe outlet opening 36, aforwardrelatively short convergent nozzle section 41 and a rear relatively longdivergent nozzle section 42 with a rear outlet opening 43 slightlylarger than the forward inlet opening 37 of the discharge conduit 34.

The nozzle 38 is provided with a plurality of axially spaced waterinjection rings or manifolds 44-47 along the divergent nozzle section42. Each water injection manifold has a plurality of equiangularlyspaced nozzles (which may be formed by apertures in the manifolds) forinjecting water into the gas stream passing through the nozzle. Thewater injection nozzles may be positioned to direct the water radiallyinto the exhaust gas or rearwardly or forwardly thereof as founddesirable in accordance with the requirements of each test cellinstallation. A suitable water conduit 49 (shown extending through oneof the nozzle supporting vanes 39) is provided for supplying water underpressure to the ring manifolds. The mass injection rate of water ispreferably controlled to reduce the temperature of the engine exhaustand water mixture in the discharge conduit 34 to approximately 212 F andsuch that the water constituent in the discharged mixture may be formedin part by water droplets and/or be readily condensed into waterdroplets for reducing the total volumetric flow rate and for assistingin removing pollutants from the discharged mixture. Accordingly,suitable flow controls (not shown) are preferably provided forautomatically controlling the water injection rate in accordance withthe power setting of the jet englne.

The injected water provides for assisting in decreasing the velocity andabating the noise of the jet engine exhaust and the divergent nozzlesection 42 is preferably designed for expanding the combined jet exhaustand water vapor (formed by the vaporization of the injected water) withminimum turbulence for assisting in attenuating the exhaust velocity andnoise.

The augmentation unit provides for augmentation of the jet engineexhaust by providing for drawing a large volume of secondary fluid intothe nozzle inlet opening 48. The secondary fluid consists of arelatively high percentage (e.g., 95 percent) of the fluid mixture fromthe rear nozzle outlet opening 43 and a relatively small percentage(e.g., Spercent) of secondary air drawn through the forward coupling 32.For this purpose the rear nozzle outlet opening 43 is made slightlylarger than the discharge conduit inlet opening 37 and the rear end ofthe shroud 30 is formed to provide a concave annular section or baffle50 surrounding the discharge conduit 34 for returning a portion of themixed jet exhaust and water constituents from the rear nozzle outletopening 43 to the forward nozzle inlet opening. Also the shroud 30 ispreferably formed to provide a forward annular baffle 51 forward of thetail pipe outlet opening 36 and contoured to direct the returned jetexhaust and water mixture rearwardly and inwardly for facilitatingaspiration of the mixture into the jet exhaust. It is preferred that asufficient portion of the jet exhaust and water mixture is returned tothe nozzle inlet to provide that the total mass flow rate of secondaryfluid (including the secondary air) approximately equals and in anyevent is no less than the mass flow rate of the jet engine exhaust.

An additional or substitute water injection system 52 (shown in brokenlines in FIG. 2) may be provided in the shroud for injecting water intothe annular return passage surrounding the nozzle 38 and for therebyadding water to the fluid being recycled to the forward nozzle inletopening, in which case the recycled fluid would preferably be cooled bythe injected water to a temperature at or below 212F and with a majorportion of the injected water remaining in the liquid state (in the formof water droplets) for subsequent rapid cooling of the jet engineexhaust within the nozzle.

The augmentation unit 10 therefore provides for attenuating the jetengine exhaust temperature and noise without the addition of asubstantial amount of secondary air as heretofore believed essential.Accordingly, the mass flow rate through the discharge conduit 34,exclusive of the injected water which is or may be readily condensed, issubstantially less than and no more than approximately half the massflow rate previously believed to be necessary. The required capacity ofthe exhaust handling equipment may therefore be substantially less thanwhat was previously required.

Three alternative embodiments 60, 70, and 80 of an augmentation unitincorporating the present invention are shown in FIGS. 3-5 respectively.In each of these embodiments a portion of the jet engine exhaust andwater mixture is returned from the rear nozzle outlet to the forwardnozzle inlet in generally the same manner as the embodiment of FIG. 2,and the embodiments of FIGS. 3-5 are shown to illustrate alternativeshroud 1 and nozzle configurations. In each of these embodiments thenozzle is shown provided with an enlarged forward throat, a relativelylong rear divergent nozzle section and a relatively short forwardconvergent nozzle section and the water injection system is shownprovided for injecting water into the divergent section of the nozzle.In FIG. 5 the outlet of the nozzle 82 is provided by a rear outletopening 84 having the same diameter as the inlet opening 37 of thedischarge conduit 34 and a plurality of radial outlet openings 86provided for returning a portion of the exhaust and water mixture to theforward nozzle inlet opening. Also, a deflector 88 is coaxially mountedwithin the discharge conduit 34 for assisting in diverting a portion ofthe exhaust and water mixture out through the nozzle outlet openings 86.I

As will be apparent to persons skilled in the art, variousmodifications, adaptations and variations of the foregoing specificdisclosure can be made without departing from the teachings of thepresent invention.

I claim:

1. A jet engine exhaust augmentation unit comprising a longitudinallyextending augmentation tube having an inlet for receiving the exhaustfrom a jet engine and an outlet, recycling means for returning a portionof the exhaust from the augmentation tube outlet for reintroduction intothe inlet thereof for combination with the jet engine exhaust, and awater injection system for injecting water into the jet engine exhaustfor lowering the temperature of the exhaust out of the augmentation tubeoutlet.

2. A jet engine exhaust augmentation unit according to claim 1 whereinthe recycling means comprises a return shroud having a forward couplingfor close coupling a jet engine thereto in alignment with theaugmentation tube.

3. A jet engine exhaust augmentation unit according to claim 2 whereinthe forward coupling provides for introducing secondary augmentation airaround the jet engine into the inlet of the augmentation tube.

4. A jet engine exhaust augmentation unit according to claim 1 furthercomprising secondary air inlet means for introducing secondary air intothe inlet of the augmentation tube for combination with the jet engineexhaust.

5. A jet engine exhaust augmentation unit according to claim 4 whereinthe total mass flow rate of the additional fluid introduced into theaugmentation tube inlet is no less than the mass flow rate of the jetengine exhaust.

6. A jet engine exhaust augmentation unit according to claim 1 furthercomprising a rear discharge conduit having a forward inlet opening inalignment with the augmentation tube for discharging from theaugmentation unit the remainder of the exhaust from the augmentationtube outlet.

7. A jet engine exhaust augmentation unit according to claim 6 whereinthe augmentation tube comprises a rear divergent nozzle section with arear outlet opening in alignment with the discharge conduit inletopening.

8. A jet engine exhaust augmentation unit according to claim 7 whereinthe rear outlet opening of the divergent nozzle section is larger thanand is spaced forwardly of the forward inlet opening of the dischargeconduit. 1

9. A jet engine exhaust augmentation unit according to claim 8 whereinthe recycling means comprises an annular concave deflector forsubstantially reversing the flow of said returned portion of the exhaustfrom the augmentation tube outlet.

10. A jet engine exhaust augmentation unit according to claim 1 whereinthe water injection system provides for injecting sufficient water toreduce the temperature of the jet engine exhaust out the augmentationtube outlet to approximately 212 F.

11. A jet engine exhaust augmentation unit according to claim 1 whereinthe water injection system provides for injecting water into theaugmentation tube for lowering the temperature of the jet engineexhaust.

12. A jet engine exhaust augmentation unit according to claim 1 whereinthe water injection system provides for injecting water into saidreturned portion of the exhaust as it is returned for reintroduction tothe tube inlet.

13. A jet engine exhaust augmentation unit according to claim 1 whereinthe augmentation tube outlet comprises a plurality of generally radialopenings in a rear portion of the augmentation tube.

14. A turbojet engine exhaust augmentation unit for a turbojet enginetest cell comprising a housing with an elongated shroud having a forwardopening for receiving a turbojet engine and a rear discharge conduitwith a forward inlet opening substantially larger than and in alignmentwith the rear exhaust opening of the turbojet engine, an elongatedaugmentation nozzle mounted within the shroud intermediate of and inalignment with the turbojet engine and discharge conduit and having aforward inlet opening for receiving the turbojet engine exhaust and arear divergent noule section with a rear outlet opening in alignmentwith and forwardly of the discharge conduit inlet opening, theaugmentation nozzle forming with the elongated shroud a substantiallyannular recirculating passage around the nozzle for returning a portionof the exhaust from the rear outlet opening of the nozzle to its forwardinlet opening, and water injection means for injecting water into theengine exhaust for lowering the temperature of the exhaust out the rearnozzle outlet opening, the augmentation nozzle being dimensioned so thatthe engine exhaust flow through the nozzle provides for drawing saidreturned exhaust portion into the nozzle inlet opening for augmentationof the engine exhaust.

15. A method of augmenting jet engine exhaust in a jet engine test cellfor reducing the exhaust temperature and noise, comprising the steps ofreturning a portion of the jet exhaust from a relative downstream pointfor aspiration into the jet engine exhaust at a relative upstream pointfor augmentation of the exhaust, and injecting water into the jetexhaust to form an exhaust and water mixture for cooling the exhaust andvaporizing the water at least in part and such that a jet exhaust andwater mixture is aspirated into the jet exhaust at said relativeupstream point.

16. A method of augmenting jet engine exhaust in a jet engine test cellaccording to claim 15 further comprising the step of aspiratingsecondary air into the jet engine exhaust at a mass flow ratesubstantially less than the mass flow rate of the exhaust and watermixture aspirated into the jet engine exhaust.

Notice of Adverse Decision in Interference In Interference No. 98AMinvolving Patent No. 3,684,054, R. D. Lemmerman, JET ENGINE EXHAUSTAUGMENTATION UNIT, final judgment adverse to the patentee was renderedJuly 18, 197 4:, as to claim 3.

[Ofiicial Gazette No vembefl' 12, 1.974.]

Notice of Adverse Dacision in Interference In Interference No. 98,414involfing Patent No. 3,684,054, R. D. Lemme]:- man, J ET ENGINE EXHAUSTAUGMENTATION UNIT, final judgment adverse to the patentee wasrenderedjJuly 18, 1974, as to claim 3.

[Ofiicial Gazette Nowembev' 12, 1.974.]

1. A jet engine exhaust augmentation unit comprising a longitudinallyextending augmentation tube having an inlet for receiving the exhaustfrom a jet engine and an outlet, recycling means for returning a portionof the exhaust from the augmentation tube outlet for reintroduction intothe inlet thereof for combination with the jet engine exhaust, and awater injection system for injecting water into the jet engine exhaustfor lowering the temperature of the exhaust out of the augmentation tubeoutlet.
 2. A jet engine exhaust augmentation unit according to claim 1wherein the recycling means comprises a return shroud having a forwardcoupling for close coupling a jet engine thereto in alignment with theaugmentation tube.
 3. A jet engine exhaust augmentation unit accordingto claim 2 wherein the forward coupling provides for introducingsecondary augmentation air around the jet engine into the inlet of theaugmentation tube.
 4. A jet engine exhaust augmentation unit accordingto claim 1 further comprising secondary air inlet means for introducingsecondary air into the inlet of the augmentation tube for combinationwith the jet engine exhaust.
 5. A jet engine exhaust augmentation unitaccording to claim 4 wherein the total mass flow rate of the additionalfluid introduced into the augmentation tube inlet is no less than themass flow rate of the jet engine exhaust.
 6. A jet engine exhaustaugmentation unit according to claim 1 further comprising a reardischarge conduit having a forward inlet opening in alignment with theaugmentation tube for discharging from the augmentation unit theremainder of the exhaust from the augmentation tube outlet.
 7. A jetengine exhaust augmentation unit according to claim 6 wherein theaugmentation tube comprises a rear divergent nozzle section with a rearoutlet opening in alignment with the discharge conduit inlet opening. 8.A jet engine exhaust augmentation unit according to claim 7 wherein therear outlet opening of the divergent nozzle section is larger than andis spaced forwardly of the forward inlet opening of the dischargeconduit.
 9. A jet engine exhaust augmentation unit according to claim 8wherein the recycling means comprises an annular concave deflector forsubstantially reversing the flow of said returned portion of the exhaustfrom the augmentation tube outlet.
 10. A jet engine exhaust augmentationunit according to claim 1 wherein the water injection system providesfor injecting sufficient water to reduce the temperature of the jetengine exhaust out the augmentation tube outlet to approximately 212* F.11. A jet engine exhaust augmentation unit according to claim 1 whereinthe water injection system provides for injecting water into theaugmentation tube for lowering the temperature of the jet engineexhaust.
 12. A jet engine exhaust augmentation unit according to claim 1wherein the water injection system provides for injecting water intosaid returned portion of the exhaust as it is returned forreintroduction to the tube inlet.
 13. A jet engine exhaust augmentationunit according to claim 1 wherein the augmentation tube outlet comprisesa plurality of generally radial openings in a rear portion of theaugmentation tube.
 14. A turbojet engine exhaust augmentation unit for aturbojet engine test cell comprising a housing with an elongated shroudhaving a forward opening for receiving a turbojet engine and a reardischarge conduit with a forward inlet opening substantially larger thanand in alignment with the rear exhaust opening of the turbojet engine,an elongated augmentation nozzle mounted within the shroud intermediateof and in alignment with the turbojet engine and discharge condUit andhaving a forward inlet opening for receiving the turbojet engine exhaustand a rear divergent nozzle section with a rear outlet opening inalignment with and forwardly of the discharge conduit inlet opening, theaugmentation nozzle forming with the elongated shroud a substantiallyannular recirculating passage around the nozzle for returning a portionof the exhaust from the rear outlet opening of the nozzle to its forwardinlet opening, and water injection means for injecting water into theengine exhaust for lowering the temperature of the exhaust out the rearnozzle outlet opening, the augmentation nozzle being dimensioned so thatthe engine exhaust flow through the nozzle provides for drawing saidreturned exhaust portion into the nozzle inlet opening for augmentationof the engine exhaust.
 15. A method of augmenting jet engine exhaust ina jet engine test cell for reducing the exhaust temperature and noise,comprising the steps of returning a portion of the jet exhaust from arelative downstream point for aspiration into the jet engine exhaust ata relative upstream point for augmentation of the exhaust, and injectingwater into the jet exhaust to form an exhaust and water mixture forcooling the exhaust and vaporizing the water at least in part and suchthat a jet exhaust and water mixture is aspirated into the jet exhaustat said relative upstream point.
 16. A method of augmenting jet engineexhaust in a jet engine test cell according to claim 15 furthercomprising the step of aspirating secondary air into the jet engineexhaust at a mass flow rate substantially less than the mass flow rateof the exhaust and water mixture aspirated into the jet engine exhaust.